All You Need To Know About 3D Printing Bionics
Exploring the world of bionic limbs and how 3D printing is revolutionizing prosthetics.
Imagine you were in a crazy car accident. Your car crashed right into the other car and you had to go to the hospital. Although you survived, you had a serious issue with your lower arm and it had to be amputated. You can’t do many of the things you used to be able to do because you don’t have part of your arm. What if you had the ability to use your arm again, you'd be able to do everything you used to be able to do. With bionics, this is actually possible, and 3D printing helps with that. 3D printing helps to make perfect sized bionic prosthetics really quickly so that people can use their limbs again. In this article I am going to explain what bionics are, the types of bionics that exist, what they are made of, and how we manufacture them with and without 3D printing.
What are Bionic Prosthetics?
Prosthetics are replacements of body parts. Basically, if you lose a leg or an arm or a hand, prosthetics are the objects that you use to replace those body parts. People have often used prosthetics if you lost a body part, but they can be anything. For example, a hook replacement for a hand is a prosthetic. Prosthetics are not always comfortable because they can literally be anything. Bionics are prosthetics, just more high tech and advanced. Bionics use tech to better connect the artificial limb or body part with the human body. Also, bionics move more like human body parts and work with the body better.
Around 30 million people need prosthetics, but many developing countries around the world do not have proper programs in place to help amputees to get prosthetics and to teach them how to use them. More than 75% of developing countries don’t have prosthetics training programs for amputees.(source).
A typical prosthetic system has three parts: the residual limb, the anchor, and the artificial limb or prosthetic. The residual limb is the limb that remains after an amputation. The prosthetic is what we think of as the artificial limb. The anchor is what connects the residual limb to the actual prosthetic. There are two primary ways to connect a prosthetic to a residual limb: a socket which cups the limb or an implant which is directly connected or implanted into the bone.
What Types Exist?
Myoelectric
Myoelectric prosthetics are a form of prosthetics that are powered by an external power source like a battery. The way that they work is they control the artificial limb using the electric signals that they can get from the muscles in the residual limb. One way that you can create myoelectric prosthetics is by putting sensors in a socket that is placed on the residual limb that can sense the electric signals. Electrical signals are sent by the wearer of the limb. The information about the electrical signals is sent to a device that then turns that information into commands that a motor can use to move the artificial limb. The person who is going to use this goes through training with the socket on. They learn how to create specific electrical signals that can be translated into specific movements with the artificial limb. They practice making those signals and learn what the different types of signals are translated into for the artificial limb.
Pros: These limbs can be created so that they have different tension depending on what they are holding. For example, someone might want a tight grip for holding a suitcase, but they would want a lighter grip if they were holding an egg.
Cons: The myoelectric prosthetics are a little heavy and bulky because they have an external battery source. This can make the prosthetic harder to use because it would take more effort to move the artificial limb. Also, there could be a delay from sending the electrical signals to making the prosthetic move. The electrical signal has to be translated into a command and then the artificial limb has to actually move based on the command and that can take longer than desired for all that to happen.
Osseointegration
The general idea of osseointegration is sticking the implant right into the bone of the residual limb. This is more stable because the implant is being directly connected to the bone. The way that they usually do this is in two parts. First, they insert the metal implant right into the bone of the residual limb. Then, sometime later after it has healed the artificial limb is connected to the implant. There are two main ways to do this, screw shape prosthesis (OPRA) and press-fit prosthetics (ILP). For the OPRA there is a screw design to the implant and it goes 80mm into the body directly into the bone. Once this procedure is done, it takes between 6 and 12 months to heal and be able to fully rely on the artificial limb. For the ILP it is a rod that goes in between 140mm and 180mm into the bone in the body. For this one, the expected recovery time is around 6 weeks which is much quicker than the OPRA. For both of them, there is rehabilitation to get used to the artificial limb for about 3 to 5 weeks.
Pros: Osseointegration allows you to have lots of movement and also allows you to have stability. With osseointegration, you are able to walk for much longer as well. There should be no skin problems are week because there is no socket, it goes right into the bone. It is pretty easy to take off and replace the actual artificial limb as well.
Cons: However, osseointegration has a long recovery time for the body to heal and grow around the implant. You have to often clean really well in between the body and the implant. Also, there is a possibility that infections can grow on the skin or even deep in the tissue of the body. Osseointegration wouldn't allow you to play high impact sports either.
What are They Made of?
In a socket based prosthetic, the socket is made to fit your residual limb like a sock is usually made of polypropylene or sometimes other fabrics. The prosthetic is usually made out of some sort of plastic and can be made out of some metals as well. The pylon is the internal structure of the prosthetic it should be lightweight so it is usually made out of some metal alloys or something like carbon fiber. The goal for the Pylon is to make it pretty light so plastics sometimes are used or titanium and aluminum alloys or carbon fiber like I said before. Sometimes a foam cover is put over the whole prosthetic to make it more lifelike as well.
How Are They Manufactured?
Different prosthetics have different parts, but generally, prosthetics have the socket, the main body of the prosthetic, and the hand or the foot to the prosthetic. Some prosthetics have batteries and motors in the main body and in the fingers, but generally, all of the prosthetics have those 3 things. To make the socket first a digital reading of the residual limb has to be made. Also, the prosthetist has to measure the different lengths of the bones and tendons in the residual limb. Then they have to make an exact replicate of the person's stump made out of plaster. After this, the prosthetist heats some thermoplastic and in a vacuum is tightly formed around the mold. Once it is tight around the mold the air is taken out of the chamber to make sure it is airtight. They then check with the amputee to make sure that the thermoplastic test fits the amputee at which point the prosthetist can heat the thermoplastic again to make little adjustments. Once the exact socket is made with the thermoplastic they can make the actual socket with polypropylene (it is done in the exact same way as with the thermoplastic test). Once the socket is made we can move onto the actual prosthetic limb where you use plastic piece liners to form the arm or leg through vacuum forming, injecting molding (forcing hot plastic into a mold), or other ways. The pylon is usually made out of aluminum or titanium whether it is pure or an alloy. If we are using the alloy’s then you would put the liquid metal through a mold so that you can get it perfect. Some of the other parts can be made with wood which can be made properly with a drill and other tools. Lastly, you use bolts and screws and put the whole prosthetic together. Adjustments can be made with screwdrivers and wrenches.
How Are They Manufactured with 3D printing?
The main way that we can manufacture 3D printed prosthetics, is by scanning the amputee's residual limb and then 3D printing the socket. The socket has to be very precise which is why you have to 3D scan it to get a perfect digital design. Once you have the design digitally, you need to 3D print it so that it fits the patient perfectly. To do this carbon fiber reinforced PLA filament or nylon filament is used to 3D print the socket. The next thing that is needed is the actual arm or leg or limb. For this, the artificial limb is often 3D printed in pieces so that it can be put together so that it can move (we don’t want the filament to be bendable so we need to put it together so that it is not stiff). Then all that is left is to 3D print the artificial limb and put it together.
Interesting Companies
Bionics Companies:
3D Printed Prosthetic Companies:
Prosthetic Covers:
Bionic Arms:
Spotlight — Open Bionics
One company making 3D printed arms is Open Bionics. Their goal is to make affordable bionic limbs that can help people who have lost their limbs. Their main product is the Hero Arm which can be just slipped on and used as a regular arm.
Hero Arm first takes a 3D scan of your residual limb and then 3D prints a new prosthetic arm for you. A socket is attached to the arm so that it is comfortable and breathable and. It is a myoelectric bionic, so it senses the muscle movement allowing you to control the arm with precision. There are batteries within the arm, and the arm is lightweight. There are also magnetic covers available that you can change when you want to. The Hero Arm is also pretty cheap and for anyone age 8 and up. There are different modes so that you can pick up light things and heavy things.
Pros/Cons of 3D Printing Bionics
Pros: The great thing about 3D printing bionics is that it is fast, cheap and pretty much anybody with a 3D printer can create one. Also if you make a great design you can keep creating the same one over and over again with a 3D printer. Another good thing is that lots of materials are becoming filaments or new 3D printers so that we can 3D print with them. You can also 3D print multiple bionic limbs on one 3D priner.
Cons: With 3D printing, most of the materials are stiff and not bendable, so you have to put the pieces together. Although there are new materials coming out for 3D printers, there still aren’t that many options for materials to use when 3D printing.
Conclusion
Bionics are high tech prosthetics that can be used to help people who lost their limbs the ability to use those limbs again. 3D printing bionics can help people to get affordable artificial limbs that can be made quickly. This whole idea can help everyone around the world who lost an arm or a leg to be able to use their arm or to be able to walk again. 3D printing bionics can really help so many people.
3D printing bionics is a pretty promising field as the upsides are much better than the downsides. 3D printing can help make bionics faster, cheaper, and possibly more diverse materials. 3D printing could one day be printing all of the bionics being used.
Resources:
- https://www.science.org.au/curious/people-medicine/bionic-limbs
- https://www.ottobockus.com/prosthetics/info-for-new-amputees/prosthetics-101/myoelectric-prosthetics-101/
- https://www.waramps.ca/pdf/english-site/ways-we-help/artificial-limbs-and-devices/upper-limb/myoelectric-arms.pdf
- https://www.amputee-coalition.org/resources/osseointegration-an-overview/
- https://scholarworks.calstate.edu/downloads/h128ng975
- http://www.madehow.com/Volume-1/Artificial-Limb.html
- https://www.hortonsoandp.com/custom-limbs-how-are-prosthetics-made/
- https://www.prescouter.com/2017/07/3d-printed-prosthetics/
- https://www.merckmanuals.com/home/special-subjects/limb-prosthetics/prosthesis-parts
